Southwestern Puerto Rico out 10NM Marine Forecast
|Today...Northeast Winds 5 To 10 Knots. Seas 1 To 3 Feet. Dominant Period 10 Seconds. Scattered Showers.|
|Tonight...Northeast Winds 10 To 15 Knots. Gusts Up To 25 Knots In The Evening. Seas 1 To 3 Feet. Dominant Period 8 Seconds. Isolated Showers.|
|Saturday...Northeast Winds 10 To 15 Knots. Seas 1 To 3 Feet. Dominant Period 7 Seconds. Scattered Showers.|
|Saturday Night...Northeast Winds 10 To 15 Knots With Gusts Up To 25 Knots. Seas 2 To 4 Feet With Occasional Seas Around 5 Feet. Dominant Period 6 Seconds.|
|Sunday...Northeast Winds 10 To 15 Knots. Seas 1 To 3 Feet. Dominant Period 7 Seconds. Scattered Showers.|
|Monday...Northeast Winds 10 To 15 Knots, Increasing To Northeast 10 To 15 Knots With Gusts Up To 25 Knots. Seas 1 To 3 Feet. Dominant Period 7 Seconds. Isolated Showers.|
|Tuesday...Northeast Winds 10 To 15 Knots. Gusts Up To 25 Knots. Seas 1 To 3 Feet. Dominant Period 6 Seconds. Isolated Showers.|
| Area Forecast Discussion|
National Weather Service San Juan PR
539am AST Fri Jan 27 2023
A shearline is causing scattered showers to pass across the northern sections of Puerto Rico and the northern USVI this morning. A pattern of shallow passing showers is expected to continue the next several days as a developing ridge in western Atlantic enhances northeast winds. Marine and coastal conditions are deteriorating due to building short-period northeasterly swell as winds strengthen over the weekend. See the marine sections below for more details.
.SHORT TERM...Today through Sunday... A shearline has arrived in the forecast area and is expected to continue past the forecast area by 28/00Z on a southwest course. There is also another cold front in the western Atlantic that is squeezing out a high pressure between the front and a low in the central Atlantic. The high pressure behind the front will continue to enhance the northeast winds that will increase during the day and increase over the area through Sunday morning. This is due to a low pressure currently at 25 north and 40 west that is sending a shallow layer of moist air toward the forecast area as the low moves to the west. Currently the GFS (Global Forecast System) shows the axis of the trough becoming nearly north-south at 29/09Z Sunday at 47 degrees west longitude. Although some drier air may pass through this afternoon and evening numerous small shallow showers are expected to be carried through the area on this northeast flow through Sunday. The greatest rainfall (up to one half inch through Sunday) is expected to be in northeast Puerto Rico and along the north coast.
Mid and upper levels, under the influence of a high pressure in the western Caribbean, are monolithically dry with little moisture even in the upper levels as an upper level ridge to the west maintains west to northwesterly flow of 10 to 25 knots.
Sunday through Friday... A high pressure system building in the western Atlantic will maintain a breezy east-northeast to northeasterly flow embedded with patchy moisture that will cause a regime of scattered showers along northern and eastern Puerto Rico and over the USVI. Due to a ridge across the mid-levels of the Caribbean Basin, dry air is dominating above 700mb which will limit any noticeable vertical lifting. This pattern will slightly change on Thursday when another high in the western Atlantic migrates eastward north of the region, returning surface winds back to an easterly flow. A perturbation in the trades may arrive on Friday, slightly increasing shower activity. After this, the positioning of high pressure to the northeast squeezed between two areas of low pressure will promote an east-southeast surface wind flow starting late Friday into the weekend. Southeastern Puerto Rico will begin to receive an increase in rainfall during this time.
All shower activity is expected to be mild with minimal rainfall accumulations. Consecutive showers over urban areas may produce ponding of water but this is not forecast to be much a concern. With northeast winds during the first half of the long term, temperatures will be slightly lower than usual as relatively cooler air advects into the region. Afterwards, the arrival of easterly flow will return temperatures back to seasonal normal values.
The arrival of a short-period northeast swell is raising sea heigheights in the local Atlantic Waters up to around 7 feet, causing the issuance of a Small Craft Advisory for the Offshore Atlantic Waters for Today until further notice. Meanwhile small craft operators across other marine zones should exercise caution. Ongoing moderate to strong northeasterly winds are the cause of this event and they are expected to strengthen over the weekend as an area of high pressure builds in the western Atlantic. Therefore, marine and coastal conditions are in a deteriorating trend.
Beachgoers should be aware that there is a a High Rip Current Risk Statement out for the northern beaches of Puerto Rico and the USVI, which includes the northern coastline from Aguadilla to Fajardo, and the islands of Culebra, St. Thomas, and St. John. The risk is moderate else where besides southern Puerto Rico, which has a low risk.
.SJU WATCHES/WARNINGS/ADVISORIES... PR...High Rip Current Risk from this evening through late tonight for PRZ001-002.
High Rip Current Risk through late tonight for PRZ005-008.
High Rip Current Risk through this afternoon for PRZ012.
VI...High Rip Current Risk through this afternoon for VIZ001.
AM...Small Craft Advisory until 6pm AST Tuesday for AMZ710.